Brake plate and method and apparatus of manufacturing same

ABSTRACT

The invention is a plate for holding a friction material in a brake assembly. The plate preferably comprises a contact surface for attaching the friction material to the plate, a second surface opposing the contact surface; and a plurality of retaining structures formed on the contact surface, each retaining structure comprising a projecting member extending from a point between the contact surface and the second surface, so that the member extends outwardly from the contact surface for engagement with the friction material.

TECHNICAL FIELD

This invention relates to brakes, and in particular to an improved brakeplate, as well as a method and apparatus for manufacturing the plate.

BACKGROUND ART

The number of motor vehicles has increased greatly in recent years.There is an interest in methods of reducing the cost of manufacturingbrakes and replacement parts on the part of both motor vehiclemanufacturers and suppliers of parts for brakes. This increased use hasalso led to a significant increase in the after-market for brakereplacement and repair. Brakes are also in increasing demand for motorvehicles such as airplanes, trains, bicycles, all terrain vehicles andmotorcycles.

Brakes, as currently manufactured, combine two main parts, namely aplate (often called a backing plate) and a friction pad, The plate ismounted in a brake assembly, and may be formed by making plate with avariety of bosses, holes, or other features for receiving and retainingthe friction pad. The need to use high speed low cost manufacturingmethods often results in irregularities in the plate which may lead todifficulties in attaching and/or retaining the friction pad on the plateduring braking, when the friction pad is in contact with the rapidlyturning brake rotor, or even during the pre-installation handling of thebrake pad assembly.

There are a variety of known ways of attaching a friction pad to aplate. One such way is to attach the friction pad to the backing platesusing rivets. One disadvantage of the riveting process is that itcreates a rigid bond between the plate and the friction pad, which can,as a result of a sudden impact, lead to breaking of the friction pad.Furthermore, this process often requires one or more additionalmanufacturing steps with a consequent increase in cost. In addition.when the friction pad is worn down over time, the rivets become exposedand rub against the brake rotor, causing scoring on the rotor which iscostly to repair.

Another, more recently developed method of mounting the friction pad onthe plate is to use a pressurised molding process to mold the frictionpad directly onto the plate. In this process, the friction pad may beprepared by blending the components of the friction pad into a pre-formor cake. A conventional pressurized molding system is used to mold thefriction pad pre-form onto the plate. A layer of cement or glue if oftenapplied to the contact surface of the plate to improve the adhesionbetween the plate and the friction pad.

As pressure is applied to the mold assembly, the pre-form becomes heatedand begins to flow, filling the mold and covering the appropriatesurface of the plate. In this process, the pre-form material is intendedto flow into and around the various features to improve the bond betweenthe plate and the friction pad.

The plate is subjected to a number of forces, such as the jarring of themoving vehicle, as well as vibration caused by the rotor and noise. Theproblem with the prior art processes and plates is that features, suchas holes and bosses, stamped into the plate often provided insufficientshear and/or tensile strength in the bond between the friction pad andplate. When additional features are stamped into the plate to increasebond strength, additional manufacturing steps are required, adding tothe cost.

The most common prior art features stamped into plates are circularholes, These holes often provide unsatisfactory results because, duringthe molding process, the pre-form cake does not completely fill all ofthe holes, which in turn, leads to deficient bonding between the plateand the preform. The incomplete hole fills can are clearly visible, andoften raise quality concerns when inspected by buyers. The incompletehole fills also have an aesthetically displeasing appearance, which canalso make them less attractive to customers. Accordingly, it has becomecommon practice in prior art plates to fill the incomplete hole fillswith putty and to paint over them, to both hide the unsatisfactorymolding results and to improve appearance. These additionalmanufacturing steps have the added disadvantage of increasing the costof manufacturing the disc brake.

Furthermore, the holes stamped by prior art processes reduce structuralstrength of the plate, and make it more vulnerable to the various forcesacting on it. These forces may distort the shape of the plate, leadingto uneven wear an the friction pad, or can lead to structural failure ofthe plate.

Another problem with brake plates is caused by the heat generated byfriction. The expansion and contraction values of the plate aredifferent from those of the friction material. Braking generates heat sothe plate and material are exposed to frequent heating and cooling.Since the expansion and contraction values differ, there may be aseparation between the plate and the material, particularly where theplate is flat or has large flat areas. Rust can then form between theplate, which leads to noise and brake failure.

Accordingly, there is a need for a brake plate and a method ofmanufacturing same which can provide improved bonding with the frictionpad without increasing the cost of producing the plate.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a plate which provides animproved bond between it and the friction pad, as well as increasing thestructural strength of the plate. without increasing the cost ofproducing the plate, In addition, it is an object of the invention toprovide a method and apparatus for manufacturing the plate which reducestime and cost by requiring fewer manufacturing steps, while at the sametime retaining the structural strength of the backing plate.

Further features of the invention will be described or will becomeapparent in the course of the following detailed description.

The invention includes a plate for holding a friction material in abrake assembly, the plate comprising:

a contact surface for attaching the friction material to the plate,

a second surface opposing the contact surface;

a plurality of retaining structures formed on the contact surface, eachretaining structure comprising a projecting member extending from apoint between the contact surface and the second surface, so that themember extends outwardly from the contact surface for engagement withthe friction material. The retaining structure may further comprise adepression surface abutting the projecting member, the depressionsurface extending into the contact surface. The contact surface may becurved or substantially flat. The brake may comprise a disk brake or adrum brake. The plate may comprise Integral retaining structures. Theretaining structures can be formed from the plate, and preferably cut orscored. In a variation, the projecting member may be a burr. The burroptionally comprises a hook shape, wherein a distal end of the hookpoints away from the depression adjacent to the hook. The retainingstructures are optionally disposed in a plurality of rows. The rows areoptionally substantially parallel. The rows may be usefully disposedlongitudinally.

The invention also includes a method of manufacturing a brake plate forsecuring a friction material to a contact surface thereof, the methodcomprising providing:

a contact surface for attaching the friction pad to the plate,

a second surface opposing the contact surface;

a plurality of retaining structures formed on the contact surface, eachretaining structure comprising a projecting member extending from apoint between the contact surface and the second surface, so that themember extends outwardly from the contact surface for engagement withthe friction pad.

The invention includes a brake plate, preferably a drum brake plate or adisc brake plate made according to a method of the invention or with theapparatus of the invention.

In one method, the retaining structures are formed by cutting thecontact surface. The retaining structures are alternatively formed byscoring the contact surface. In another variation, the retainingstructures are formed by cutting a plurality of rows of retainingstructures on the contact surface. The rows are optionally substantiallyparallel and/or disposed longitudinally.

In one embodiment, the cutting is done by a plurality of knives, eachknife having a cutting edge, the edge having a plurality of teethconnected thereto. Each retaining structure is preferably made by onetooth. Each tooth preferably cuts a projecting member from the contactsurface to form an adjacent depression. The knives are preferablydisposed longitudinally in relation to the plate. The knives may besubstantially parallel. Adjacent knives preferably move in opposingdirections. The plurality of knives are preferably moving parallel tothe contact surface prior to impacting the plate The plurality of knivespreferably commence to move parallel to the contact surface upon impactwith the plate. The plate may be stationary while it is punched by theknives, The knives are optionally fixed in the direction perpendicularto the contact surface and the plate is impacted onto the knives.

Another variation of the invention relates to an apparatus formanufacturing a brake plate having a plurality of retaining structuresformed on a contact surface thereof for retaining a friction material,comprising:

a means for cutting a plurality of retaining structures on the contactsurface, each retaining structure comprising a projecting memberextending from a point between the contact surface and the secondsurface, so that the member extends outwardly from the contact surfacefor engagement with the friction pad, the cutting means being adapted tomove generally parallel to the contact surface to cut the retainingstructures;

a driving means for impacting the cutting means and the contact surfaceof the plate to form the retaining structures.

The cutting means preferably comprises a plurality of knives, each knifehaving a cutting edge, the edge having a plurality of teeth connectedthereto, each tooth adapted to form one of the plurality of retainingstructures upon impact with the contact surface,

The apparatus optionally further comprises:

at least one drive member slidably connected to at least one side ofeach of the plurality of knives;

at least one slide member slidably connected to the drive member;

During impact between the knives and the contact surface, the slidemember is preferably adapted to move away from the contact surface, theslide member being adapted to move the drive member generally parallelto the contact surface, the drive member being adapted to move theknives generally parallel to the contact surface.

The slide member may have an inclined sliding surface, the slidingsurface being adapted to move the drive member generally parallel to thecontact surface upon movement of the slide member. The at least oneslide member can be two slide members, the at least one drive member cancomprise first and second drive members, and the at least one side ofthe each of the knives can comprise a first side and a second side,wherein first drive member is proximate to the first side of at leastone knife, and the second drive member is proximate the second side ofthe remaining knives. The first and second sides of alternate knives arepreferably proximate to the first and second drive members,respectively. The adjacent knives preferably move in opposing directionsupon impact with the contact surface. The apparatus may further comprisea return means for returning the knives to a starting position. Thereturn means is optionally at least one spring attached to a first andsecond slide rod, the slide rods being located within a first and secondguide slots defined proximate to the first and second side of eachknife. The plurality of knives are preferably disposed longitudinally inrelation to the plate, The apparatus knives are preferably substantiallyparallel to each other.

The slide member and the plurality of knives are preferably adapted tomove generally parallel to the contact surface prior to impact with theplate. The plurality of knives are preferably adapted to move parallelto the contact surface upon impact with the plate. The plate isoptionally stationary while punched by the knives. The knives areoptionally fixed in the direction perpendicular to the contact surface,and the plate is driven onto the knives. The impacting means optionallycomprises a press having a top movable portion and a bottom stationaryportion.

The apparatus of optionally further comprises:

a base plate secured to the top portion of the press;

two side plates secured to the base plate, the side plates projectingdownwardly therefrom;

a positioning means for maintaining the knives in proximate to eachother; the positioning means being connected to the side plates;

a force adjustment means for adjusting the force of impact of the knivesagainst the contact surface, the force adjustment means having apressure plate generally parallel to the base plate and at least onespring disposed between the base plate and the pressure plate, thepressure plate being connected to the knives;

wherein the first and second slide rods are suspended from the baseplate.

The first and second sliding members preferably impact the bottomportion of the press prior to the knives impacting the contact surface,thereby causing the knives to move generally parallel to the contactsurface prior to impact of the knives against the contact surface. Thefirst and second sliding members preferably impact the bottom portion ofthe press substantially simultaneously with the knives impacting thecontact surface, thereby causing the knives to move generally parallelto the contact surface substantially simultaneously with impact of theknives against the contact surface.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood, preferredembodiment thereof will now be described in detail by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a preferred embodiment of a plateaccording to the present invention:

FIG. 2 is a perspective view of a preferred embodiment of an apparatusfor manufacturing the plate according to the present invention;

FIG. 3A is a plan view of the apparatus;

FIG. 3B is a magnified view showing the knives and teeth of theapparatus shown in FIG. 3A;

FIG. 4 is an elevation view of the apparatus with the side platesremoved:

FIG. 5A is a cross-sectional view showing the apparatus impacting thebottom of a conventional press;

FIG. 5B is a cross-sectional view showing the knives beginning to cutinto a blank;

FIG. 5C is a cross-sectional view showing the knives completing the cutinto a blank;

FIG. 5D is a cross sectional view showing the apparatus impacting apress. The spring is beneath the press. A spring or a nitro spring maybe used.

FIG. 6 is a perspective view of an alternate preferred embodiment of aplate according to the present invention;

FIG. 7 is a perspective view of a preferred embodiment of a knife withrows of offset teeth for manufacturing the backing plate according tothe present invention, The figure shows an insert allowing one or moreteeth to be releasably inserted into the knife.

FIG. 8A is a top plan view of a knife;

FIG. 8B is a side plan view of a knife;

FIG. 8C is a top plan view of a knife;

FIG. 8D is a side plan view of a knife;

FIGS. 9A and B are perspective views of a releasable knife insert havingoffset teeth;

FIGS. 9C is a perspective view of a releasable knife insert.

DETAILED DESCRIPTION OF THE INVENTION

The invention is a plate for holding a friction material in a brakeassembly. The plate preferably comprises:

(a) a contact surface for attaching the friction material to the plate,

(b) a second surface opposing the contact surface;

(c) a plurality of retaining structures formed on the contact surface,each retaining structure comprising a projecting member extending from apoint between the contact surface and the second surface, so that themember extends outwardly from the contact surface for engagement withthe friction material.

The retaining structure may further comprise a depression surfaceabutting the projecting member, the depression surface extending intothe contact surface.

The brake plate, as well as the process and apparatus for manufacturingsame according to the present invention are useful in the field ofmanufacturing of vehicle brake parts. The plate is useful in brakes forany motor vehicle, such as cars, trucks, airplanes, trains, bicycles,all terrain vehicles or motorcycles.

FIG. 1 shows a brake plate 1 according to a preferred embodiment of thepresent invention. The plate 1 has a conventional shape and any suitablethickness (⅛-½ of an inch), and is preferably manufactured from metal ora metal composite adapted to withstand the rigors of a conventionalbraking system. The circular holes shown on the plate are not necessaryand are included for illustrative purposes only. The backing plate has acontact surface 2 for molding a friction material (not shown) thereto bya conventional molding process.

Any suitable number of retaining structures 3 are connected to the firstsurface of the backing plate. Preferably, the retaining structures areintegrally formed by punching the backing plate, as described in moredetail below. Each retaining structure includes a burr 4 projecting outof the first surface, which is located adjacent to a correspondingdepression 5 defined in the contact surface 2. Preferably, each burr isintegrally formed by cutting the burr out of the first surface of thebacking plate, which creates the corresponding depression 6. Theprojecting member extends from a point between the contact surface andthe second surface 36 (in FIG. 6, the second surface is opposite thecontact surface and appears as the flat bottom surface of the plate), sothat the member extends outwardly from the contact surface forengagement with the friction material. Each burr preferably has a curvedshape, which curves away from its corresponding depression.

The retaining structures 3 are preferably arranged in longitudinallydisposed substantially parallel rows 6. Preferably, the position of theburr 4 and depression 5 is identical for each row, but alternates withadjacent rows, as shown in FIG. 1. Preferably, the number of rows issufficient to cover substantially the entire surface area of the backingplate 1 in order to provide maximum bond strength. The depth of thedepressions and the height of the burrs depends on the bond strengthrequired for a particular application. FIG. 6 shows a variation of theplate in which there is increased space between the structures of eachrow. The retaining structures in each row are spaced apart farther thanthose in FIG. 1.

The plate 1 according to the present invention does not need to becoated with an any adhesive to achieve the required bond strength withthe friction material. Since the plate has a large number of projectingmembers, there will be no separation between the plate and the materialas the plate and material are subjected to frequent heating and cooling.The plate lasts longer and is safer.

For a disc brake as shown in FIG. 1, the height of the members maypreferably be about 0.030 inches to 0.075 inches above the contactsurface. There are preferably at least about 20 projecting members persquare inch. The horizontal pitch (distance between each member) betweenmembers in the direction of chip formation may preferably range between0.120 and 0,250 inches. The pitch between rows is preferably about 0.100to 0.200 inches. The coverage of members on the contact surface ispreferably at least about 65% for a disc brake.

For a disc brake as shown in FIG. 6, the height of the members maypreferably be about 0.030 inches to 0.075 inches and more preferablyabout 0.045 to 0.060 inches above the contact surface. There arepreferably at least about 30 projecting members per square inch. Thehorizontal pitch (distance between each) between members in thedirection of chip formation may preferably range between 0.120 and 0.250inches and is more preferably 0.060 inches. The coverage of members onthe contact surface is preferably at least about 65% for a disc brake.

The method of manufacturing the backing plate 1 according to the presentinvention comprises placing the backing plate on a flat surface under aconventional press and punching the contact surface 2 of the backingplate with a series of substantially parallel knives 10. Referring toFIG. 2, the knives are preferably disposed substantially parallel to thelongitudinal axis of the backing plate. Each knife has a plurality ofpreferably identical teeth 11 defined along a cutting edge thereof. Eachtooth forms the depression 5 and burr 4 of one retaining structure 3.The configuration of the teeth may alternate from row to row, such thatevery other row has an identical configuration. In FIG. 6, a knife withoffset teeth is preferably used to create a checkerboard pattern(alternating retaining structure pattern) between rows cut by the sameknife.

FIG. 2 shows the apparatus 12 for manufacturing the backing plateaccording to the present invention. The apparatus is mounted to aconventional press in any suitable manner for punching the backing plate1, as described above.

Referring to FIGS. 2-4, the apparatus 12 includes a base plate 13 fromwhich two side plates 14 are suspended by preferably four conventionalscrews 15. Preferably, two transverse slide rods 16 are suspended fromfour support springs (not shown) which are each attached to one of thescrews at one end and to an end of the slide rod at the other end. Theslide rods are slidably secured to the knives 10 by preferably locatingin guide slots 17 defined in the knives. A biasing means, such as, forexamples two return springs 18 are connected to each slide rod to biasthe slide rods toward each other. A pressure plate 19 is disposed abovethe non-cutting edges of the knives. Preferably, a plurality ofadjustment springs 20 are disposed between the base plate and thepressure plate to urge the two apart. Two block housings 21 are mountedtransversely onto the base plate adjacent to the edges of the knives. Adrive block 22 is mounted on each block housing by a slide bolt 23 whichis disposed substantially parallel to the longitudinal axis of theknives. A slide block 24 is slidably mounted in each housing adjacent tothe drive block.

FIG. 5A shows the initial step of operation of the apparatus 12. Aconventional press (not shown) drives the apparatus 12 onto a plateblank 25, such that the slide block 24 preferably impacts the bottomsurface of the press 26 before the knives 10 impact the blank. Theimpact against the bottom surface of the plate drives the slide block uprelative to the drive block 22, causing the slide block sliding surface27 to exert a force on the drive block substantially parallel to thelongitudinal axis of the knives. This force causes each drive block tomove alternate knives along their longitudinal axis. Because onlyalternate knives contact each drive block before impact, adjacent knivesare pushed in opposite directions by each drive block. Preferably, theknives are moving before the blank contacts the knives.

The teeth of the knives may be arranged along the longitudinal axis ofthe knife, so that they form a single row. There may be portions whereno teeth are present, as in FIG. 8D. Each tooth has a leading surfacewhich is transverse to the axis of the knife. The leading surface may beangled to determine the burr shape, in the same manner as a plow isangled. All the teeth may have a similar leading angle or they may bevaried.

In a knife variation, the teeth are offset, preferably so that the teethare arranged in two or more rows, as shown in FIG. 9. Each knife thuscuts rows of teeth along two longitudinal axes (forming two rows thatare preferably substantially parallel) to provide a brake pad as shownin FIG. 6.

Referring to FIGS. 5B and 5C, the impact of the knives 10 against theblank 25 may be regulated by the biasing means, preferably adjustmentsprings 20 (shown in FIG. 2). The adjustment springs allow the apparatus12 to be mounted on presses having different force specifications. Theadjustment springs effectively ensure that a constant force is exertedagainst the knives, regardless of the force applied by the press. In avariation, the springs are located beneath the plate as shown in FIG.5D. As the knives are pushed down into the blank, they also slide alongthe slide rods 16 parallel to their longitudinal axis, such thatadjacent knives are moving in opposite directions as they cut. Thesesimultaneous downward and sliding movements cause each tooth 11 of aknife to form one retaining structure 3.

The apparatus is able to complete an entire plate in one punch. Afterthe press lifts the apparatus 12, the slide block 24 is returned intoits starting position by gravity, and the knives 10 and drive block 22are returned to their starting positions by the slide springs 19. Oneskilled in the art could readily use the knives to prepare drum brakeplates.

During the process of molding and securing the friction material to theplate, the pre-form material is set into a mold and pressed against theplate. The material flows into and surrounds each retaining structure 3to bond with the plate 1. The retaining structures provide improvedtensile strength, as well as providing improved shear resistance. Thetensile and shear strengths can be varied by changing either the depthof the cut (i.e. the depression 5), which also increases the height ofthe burr 4. These results are accomplished using a two step process, andwithout the need for additional features, such as holes, leading to adecreased manufacturing time and significant cost savings.

FIG. 5D shows a variation of the apparatus in which a spring is mountedon a fixed press bed so that the spring is beneath the press. The springmay be a conventional coil spring or a nitrogen spring. Any othersuitable biasing means may be used. A knife of the invention is shown inFIGS. 7 and 8. In these figures, the teeth of each knife are alignedalong an axis defined by the knife. However, the teeth may be offset toprovide a brake pad of the type shown in FIG. 6. FIG. 7 shows a knifewith offset teeth.

FIG. 7 also shows that the knife may be made with releasable inserts.Broken or dull teeth may be readily changed without discarding theknife, A blank insert with no teeth may also be used. Inserts mayoptionally be permanently fixed in the knife. FIGS. 8A and 8B show theknife with continuous teeth. FIGS. 8C and 8D show the knife having ablank surface where no teeth are present. The plate will have noretaining surfaces formed where the knife is blank. FIGS. 9A and 9B showoffset teeth. FIG. 9C shows that the offset teeth are preferably aboutthe same height above the knife.

It will be appreciated that the above description relates to thepreferred embodiment by way of example only. Many variations on theinvention will be obvious to those knowledgeable in the field, and suchobvious variations are within the scope of the invention as describedand claimed, whether or not expressly described.

What is claimed is:
 1. A plate for holding a friction material in abrake assembly, the plate comprising: (a) a contact surface, and (b) aplurality of parallel rows of integral retaining structures formed onthe contact surface, each row defining a longitudinal axis along theplate, each retaining structure comprising a projecting member extendingoutwardly from the contact surface for engagement with the frictionmaterial; and wherein the area of the plate covered by retainingstructures comprises an area approximately equal to the area of thefriction material to be coupled to the plate; and wherein at least oneside of the plate is not parallel to any other side.
 2. The plate ofclaim 1, wherein each retaining structure further comprises a depressionsurface abutting the projecting member, the depression surface extendinginto the contact surface.
 3. The plate of claim 2, wherein thedepression surface has a length at least double the height of itsabutting projecting member.
 4. The plate of claim 1, wherein each row ofretaining structures comprises spaced apart retaining structures, theretaining structures being positioned so as to form a staggeredconfiguration between adjacent rows.
 5. The plate of claim 4, whereinthe plate comprises a plurality of pairs of rows of retainingstructures, each pair of rows comprising a first row comprisingretaining structures angled in a first sideward direction and a secondrow comprising retaining structures angled in a second opposite sidewarddirection.
 6. The plate of claim 1, wherein the contact surface iscurved or substantially flat.
 7. The plate of claim 1, wherein the plateis a disk brake plate or a drum brake plate.
 8. The plate of claim 2,wherein the projecting member is in the form of a hook, the hook beingdirected away from the abutting depression surface.
 9. A plate forholding a friction material in a brake assembly, the plate comprising:(a) a contact surface, and (b) a plurality of parallel rows of integralretaining structures formed on the contact surface, each row defining alongitudinal axis along the plate, each retaining structure comprising aprojecting member extending outwardly from the contact surface forengagement with the friction material; and wherein each retainingstructure further comprises a depression surface abutting the projectingmember, the depression surface extending into the contact surface; andwherein the depression surface has a length at least double the heightof its abutting projecting member.
 10. A plate for holding a frictionmaterial in a brake assembly, the plate comprising: (a) a contactsurface, and (b) a plurality of parallel rows of integral retainingstructures formed on the contact surface, each row defining alongitudinal axis along the plate, each retaining structure comprising aprojecting member extending outwardly from the contact surface forengagement with the friction material; and wherein each row of retainingstructures comprises spaced apart retaining structures, the retainingstructures being positioned so as to form a staggered configurationbetween adjacent rows.
 11. The plate of claim 10, for holding a frictionmaterial in a brake assembly, the plate comprising: (a) a contactsurface, and (b) a plurality of parallel rows of integral retainingstructures formed on the contact surface, each row defining alongitudinal axis along the plate, each retaining structure comprising aprojecting member extending outwardly from the contact surface forengagement with the friction material; and wherein each row of retainingstructures comprises spaced apart retaining structures, the retainingstructures being positioned so as to form a staggered configurationbetween adjacent rows; and wherein the plate comprises a plurality ofpairs of rows of retaining structures, each pair of rows comprising afirst row comprising retaining structures angled in a first sidewarddirection and a second row comprising retaining structures angled in asecond opposite sideward direction.